1. Field of the Invention
The present invention relates generally to the manufacture of semiconductor devices, and, more particularly, to a high-resolution lithographic method for the microfabrication of semiconductor devices.
2. Description of the Related Art
The continuing need for higher-integration and higher-density semiconductor devices has resulted in a variety of improvements relating to the method of pattern transfer, which is mainly based upon microlithography, for forming micron- or submicron-order fine patterns in electronic devices such as semiconductor devices.
One of these improvements is the so-called surface-imaging method, which uses an image of the highest quality as a resist pattern on the exposure surface of a photoresist. An example of this method is described in Schellekens et al, "Single Level Dry Developable Resist Systems, Based on Gas Phase Silylation." SPIE, Vol. 1086, Advances in Resist Technology and Processing VI (1989), pp. 220-228. In this example, deep ultraviolet radiation is applied to a desired portion of a chemical amplification resist layer, and then the portion of the resist layer is heated to cross-link it. Then, those portions of the resist layer to which deep ultraviolet radiation is not applied are silylated. Afterward, the resist is dry-etched by using the silylated portion as a mask to form a resist pattern.
This method has proven generally effective because of the structure of the chemical amplification resist layer. The chemical amplification resist layer comprises a single pattern-forming layer material for producing a catalyst in latent image-forming portion of the resist by applying actinic radiation, such as ultraviolet radiation, in accordance with a pattern, thus causing the solubilities of radiation-applied and nonradiation-applied portions of the latent image-forming portion to differ from each other. The catalyst encourages the reaction that results in the latent image pattern being formed in the latent image-forming portion.
Because the silylated portion is formed in an exposure surface with the highest image quality, a two-dimensional image of the silylated portion is transferred to the resist pattern. As a result, the influence of the exposure profile in the film-thickness direction is small compared with that of the ordinary resist pattern-forming methods, in which development is performed in accordance with a three-dimensional exposure state. That is, the lateral line of the pattern profile is a straight line approximately vertical to the bottom surface of the resist layer. Therefore, transformation of the pattern profile is reduced.
Thus, the conventional surface imaging methods allow the accurate dry etching of step substrates and other types of substrates, and also hybrid lithography, using a plurality of radiation sources. However, the conventional methods require batch processing for silylation. This is a disadvantage in industrial production, which is based on continuous processing.